# Tetragon (EntityTopic, 7)

(Redirected from Rhombus)

A tetragon is a two-dimensional shape with four straight edges. There are several variations of the tetragon.

## Square

A square is the most constrained tetragon having all edges the same length and all angles being 90 degrees. It has four lines of symmetry - horizontal, vertical and two diagonals - plus order four rotational symmetry.

## Rectangle

A rectangle has opposite edges the same length and all angles 90 degrees. It has two lines of symmetry - horizontal and vertical - plus order two rotational symmetry. All squares are rectangles.

## Rhombus

A rhombus has all edges the same length and opposite angles equal. It has two lines of symmetry - two diagonals - plus order two rotational symmetry. The rhombus is dual with the rectangle. All squares are rhombi. Lathing a rhombus around one of its lines of symmetry produces a bicone.

## Parallelogram

A parallelogram has opposite edges the same length and opposite angles equal. It has order two rotational symmetry. All rectangles and rhombi are parallelograms. Lathing a parallelogram around any of its edges produces a cylindrogram.

## Trapezium

A trapezium has two pairs of adjacent, equal angles, with the two edges connecting the pairs of equal length, and the other two edges parallel to each other. It has one line of symmetry - the line containing the midpoints of the two parallel sides. All rectangles are trapeziums. Lathing a trapezium around its line of symmetry produces a frustum; lathing it around its longer edge produces an expanded bicone.

## Kite

A kite has one pair of opposite angles equal, with the other pair not equal. As such, the two edges adjacent to one of the unequal pair of angles share an equal length, as do the remaining two edges. It has one line of symmetry - the line containing the pair of points of unequal angles. All rhombi are kites.

## Arrow

An arrow is a kite with one angle reflex. Its symmetry is the same as the kite. Lathing an arrow around its line of symmetry produces an arrinder.